Wireless communications systems provide wireless service to a number of wireless or mobile units situated within a geographic region. The geographic region supported by a wireless communications system is divided into spatially distinct areas commonly referred to as “cells.” Each cell, ideally, may be represented by a hexagon in a honeycomb pattern. In practice, however, each cell may have an irregular shape, depending on various factors including the topography of the terrain surrounding the cell. Moreover, each cell is further broken into two or more sectors. Each cell is commonly divided into three sectors, each having a range of 120 degrees, for example.
A conventional cellular system comprises a number of cell sites or base stations geographically distributed to support the transmission and reception of communication signals to and from the wireless or mobile units. Each cell site handles voice communications within a cell. Moreover, the overall coverage area for the cellular system may be defined by the union of cells for all of the cell sites, where the coverage areas for nearby cell sites overlap to ensure, where possible, contiguous communication coverage within the outer boundaries of the system's coverage area.
Each base station comprises at least one radio and at least one antenna for communicating with the wireless units in that cell. Moreover, each base station also comprises transmission equipment for communicating with a Mobile Switching Center (“MSC”). A mobile switching center is responsible for, among other things, establishing and maintaining calls between the wireless units, between a wireless unit and a wireline unit through a public switched telephone network (“PSTN”), as well as between a wireless unit and a packet data network (“PDN”), such as the Internet. A base station controller (“BSC”) administers the radio resources for one or more base stations and relays this information to the MSC.
When active, a wireless unit receives signals from at least one base station over a forward link or downlink and transmits signals to at least one base station over a reverse link or uplink. Several approaches have been developed for defining links or channels in a cellular communication system, including time division multiple access (“TDMA”), frequency division multiple access (“FDMA”), orthogonal frequency division multiple access (“OFDMA”) and code division multiple access (“CDMA”), for example.
For voice applications, conventional cellular communication systems employ dedicated links between each relevant wireless unit and a corresponding base station. Voice communications are delay-intolerant by nature. Consequently, wireless units in wireless cellular communication systems transmit and receive signals over one or more dedicated links. Each active wireless unit, as a result, generally requires the assignment of a dedicated link on the downlink, as well as a dedicated link on the uplink.
With the explosion of the Internet and the increasing demand for data, resource management has become a growing issue in cellular communication systems. Unlike voice, however, data communications may be relatively delay tolerant and potentially bursty in nature. Data communications, as such, may not require dedicated links on the downlink or the uplink, but rather enable one or more channels to be shared by a number of wireless units. By this arrangement, each of the wireless units on the uplink competes for available resources. Resources to be managed in the uplink include the received power at the base station, and the interference created by each user to other users in the same sector or cell, as well as in other sectors or cells, for example. This is in contrast to the resources to be managed on the downlink, including fixed transmit power budgets.
One byproduct of the explosion in data applications is an increase in traffic. More particularly, data traffic growth over the uplink raises concerns regarding overload. An overload condition may cause increased interference, thereby degrading system performance. For the purposes of the present disclosure, an overload condition refers to a condition wherein one or more new users are denied access to the wireless network over the uplink. Heavy data traffic over the uplink may cause an overload condition, forcing a new user to wait either for an “in” network user to exit the network and/or for the system to terminate an “in” network user's access, based on inactivity or priority, for example. Moreover, once a new user is granted access to the network in heavy traffic, the data transmission rate afforded to each user over the uplink may depend on the air interface, as well as interference, taking degrading system conditions into consideration.
Consequently, a demand exists for a method that addresses the concerns surrounding overload and system performance degrading over the uplink. A need further exists for a method that supports increased user access over the uplink in an overload condition. Moreover, a demand exists for a method that may vary data transmission rate afforded to each user over the uplink if the network is in an overload condition.